The invention relates to a driver for feeding thin metal sheets on a can welding machine, having
a carrier for attachment to a conveyor, and PA1 a pusher made of hard-wearing material and attached to the carrier in such a way that when the latter moves forwards it engages a rear edge of a metal sheet to be fed.
Drivers of this type are for example attached to continuously or intermittently circulating conveyor chains as described in U.S. Pat. Nos. 4,824,007 and 4,870,241 owned by the assignee of the present invention. For this purpose the drivers may be constructed so as to each replace all or part of a link of chain. On conventional drivers of this type, the carrier is made of steel and has in its front surface a depression shaped like part of a cylinder, to which a cylindrical pusher made of ceramic material is cemented.
Such drivers are used on can welding machines chiefly to push cylindrical can bodies rounded from a corresponding rectangular sheet blank in a rounding apparatus along a welding arm into a welding station, where they pass between electrode rollers to produce a longitudinal seam. In this manner it is possible to round and weld 300 to 600 or even more bodies per minute from metal sheet of, say, 0.2 mm thickness.
Two or more drivers take up each of the can bodies at the exit from the rounding apparatus and in a short time accelerate them to the welding speed, which for a given number of bodies per unit of time is greater the longer are the bodies. Particularly in the case of long can bodies made of thin metal sheet, the forces necessary for acceleration may become so great that the drivers produce indentations on the rear edges of the bodies. While such indentations do not affect the welding of longitudinal seams on the bodies, they can be a nuisance subsequently when the lid and base are flanged onto each can body.
To prevent such indentations it has hitherto been necessary to either limit the number of can bodies fed per unit of time and hence underutilize the welding station or to provide a comparatively long conveyor line in order to accelerate the bodies gradually.